Electrical gauging and sorting apparatus utilizing standing waves



p 1953 M. M. ARLIN ELECTRICAL GAUGING AND SORTING APPARATUS UTILIZINGSTANDING WAVES Filed June 24, 1947 4 Sheets-Sheet l BY ,7 W4, M-

rro/TNEYS.

April 21, 1953 M. M. ARLIN ELECTRICAL GAUGING AND SORTING APPARATUSUTILIZING STANDING WAVES 4 Sheets-Sheet 2 Filed June 24, 1947 a z y u MZ W a aw 4% .1,

INVENTOR. fi/ax M fir/z'zz.

OFA/E/SZ- Aprll 21, 1953 M. M. ARLIN 2,635,748

ELECTRICAL GAUGING ND SORTING APPARATUS UTILIZING STANDING WAVES FiledJune 24, 1947 4 Sheets-Sheet 5 Z/a X ll 7 U y g3 ,24

2J4 l v 2 3 INVENTOR. MK M Fr/z'rz.

April 21, 1953 M M ARLIN 2,635,748

ELECTRICAL GAUGING'AND SORTING APPARATUS UTILIZING STANDING WAVES 4Sheets-Sheet 4 Filed June 24, 1947 0 4 7T in I INVENTOR.

Max M #r/z'n.

Patented Apr. 21, 1953' orrie-E ELECTRICAL GAUGING -SOR'IING APPARATUSUTILIZING STANDING WAVES .Max'M. Arlin, Dctroit, -Mich.

Application :Iune24, 1947,Serial No."75'6;591

121Claims. 1 The 'present invention relates to :measuring systemsandmore particularly to such systems wherein a measurement-of a physicalcharacteristic of a workpiece 'isobtained by enablingsuch-cha-racteri-stic to determine'the value of an impedance included inan electrical network which I also includes an electrical measuringinstrument. 'In the-specific 'formdisclosed herein,"-the invention-isparticularly adapted for electrical gauging operations, and affords aneconomieal and "reliable 'unit for detecting variations, =in'physicaldimensions, of magnitudes as lowas-one millionth of an inch.

This-application isa continuation in part :of my co-pending applicationSerial No. 56L020 filed October 3 0, 1944, for Electric Measuring systemnow abandoned.

Principal objects of the present invention are to-provide asystem whichrepresents'patentable advance "both in respectto its metho'd-and itsapparatus, and which issimplein arrangement, economical of manufactureand assembly and which is reliable in operation; to provide such asystem which, in a generic sense, comprises anoscillatorysource,a-measuring network coupled thereto,-'and a variable impedanceelementwhichis' effective -'-to determine the frequency: of the source and toconsequently determine the amplitude "of pulsations in the measuringnetwork, suchnetwork including-a-measuring device responsive to suchamplitude; -to; prov-ide an improved '-combination *of --circu-itcontrolling -elements 'whereby-"the response of the -measuring device*is; linear with respect to linear changes in-the mea-suredcharacteristic of the workpiece; to provide improved constructions ofvariable condensers for use in systems of the above as well as othertypes; to provide a network responsive to the pulsations in themeasuring network for selectively controlling the disposition of themeasured workpiece; to provide-such a segregating network which willsegregate the workpieces according to the magnitude of'thecharacteristic; to provide in such a segregating network means'to holdthesegregating gatesintheir-set position until the workpiece has beendiverted thereby; and to generally improve the constructionandarrangement of systems of the above generally indicated character.

fWith the above as well as other and more detailed objects in view,which appear in the following description and in the appended claims, apreferred but illustrative embodiment 40f 'the' invehtionjs shown intheaccompanying drawing; throughout the several views of which "cor- .2responding referencecharacters are used to designate corresponding partsand in which:

Figure 1 is a diagrammatic view of an -electrical control systemembodying the invention; i Fig. 2 is .-.-a view, partly in -section,-ofa pre-- ferr-ed variable condenser gauging head;

Fig. "'3 a viewin section, taken along the lines- 3 of Eigure z;

Fig. 4 is agraphic-representationof -a typical condenser capacity-=curve;

Fig. "=5 is a graphic representation of -a typical resonance curve;

Fig. G is agraphic -representationof the-standing-wa-ves setupbytheoscillator and *schematisegregating apparatus showndiagrammatically in'Fig. '7; "Fig.9 is a view insubstantialcentralvertical section with certain of the parts in elevationillustrating a modifiedform'of gauge head;

Fig. I0 is a View taken substantially along the line lll0 of Fig. 9 andlooking in thedirection of i the arrows; and

*Fig. 1-1 -is a fragmentary diagrammatic view ,of-a modified form of'the segregator control network :foruse with vathe system of :Fig. 7.

Referring first to "Figure 1, the system comprises :generally "an.oscillatory network to, a measuringnetwork &2, and a source SM of:electrical -:energy.

Thmsource I 4 may-be conventionally arranged to 'impressasubstantially-uniform-direct current E. M. F. across the inputterminals l6 :and 5118 of the oscillatory :network it. shown, (thesource comprises a supply transformer 29, -the primary winding whereofis subject to control by usual control switch 22, :and the terminalsof-the center-tapped secondary winding whereof are connected -'-to theanodes of a usual rectifier 24 which may be, "for example; of the type"known to the trade'as'a 53 -rectifier. The cathode of rectifierfl isconnected through aregulating --resistor -=26,to terminal It. The centertap 28 isccnnected to the cathode of rectifier 2 through a"potentiometer resistor -30, tap 32 whereof is*connectedto'terminal18. Ausual filter condenser 34 and a-pair-of usual :glow'tube regulatingvalves *36 are connected *across terminals [1'5 and {8 -in--usual:fashion.

'From the-*foregoing-ivwill be understood that 3 the perhaps variablevoltage of transformer 20 is translated into a substantially uniformdirect current E. M. F., for application to the input terminals I6 andI8 of the oscillatory network I 0.

The oscillatory network I may be of any suitable conventional type,adapted to deliver energy at a suitable high frequency. The presentsystem is primarily designed, as aforesaid, to produce a usable signalin response to changes in physical dimensions ranging in magnitude froma few thousandths of an inch down to one or more millionths of an inch.In order to maintain the physical dimensions of the condenser 40,associated with the hereinafter described gauge head, at practicalvalues accordingly, it is preferred to operate the system at frequenciescorresponding to wave lengths of the order of 10 meters or less. In thebroader aspects of the invention, considerably lower frequencies areusable. As a specific example, in measuring physical changes of theorder of a few thousandths of an inch, an oscillator frequency having awave length of approximately three meters has been found satisfactory.In measuring smaller physical changes, of the order of one or moremillionths of an inch, it has been found desirable to utilize anoscillator frequency of the just-mentioned order, and to tune themeasuring circuit I2 to respond to a harmonic of the oscillatorfrequency.

The illustrated oscillatory network I0 includes a usual oscillator valve42 of the screen grid type, and which may be, for example, of the typeknown to the trade as a 6L6 tube. The grounded cathode c of valve 42 isdirectly connected to terminal I8.- The anode a. of valve 421s connectedthrough a portion of a usual tank coil 44, and a usual radio frequencychoke 46, to terminal IS. The remaining portion of tank coil 44 iscoupled to the control grid 9 of valve 42 through a condenser 41. Grid gin turn is connected to the cathode through a resistor 48. It will beappreciated that terminal 50 on the tank coil 44 is at the nodal pointthereof. The screen grid s of valve 42 is connected to terminal I6 andis also coupled to terminal I8 through a usual filter condenser 52.

With the foregoing arrangement, it will be appreciated that the networkI0 translates the input energy applied to terminals I6 and I8, into anoscillatory output, the frequency and amplitude whereof are determinedby the magnitudes of the impedances in the network I0 as well as themagnitudes of the irnpedances included in the measuring network I2.Accordingly, the potential of the oscillator terminal 54 pulsates, aboveand below ground potential at the justmentioned frequency.

The measuring network includes a usual diode rectifier 56 which may be,for example, of the type known to the trade as a 61-16 rectifier.- Theanodes of rectifier 56 are coupled to terminal 54 through a conductor58, a usual coupling condenser 60, and a variable trimmer or tuning con-The meter terminal 68 is grounded,-

indicated polarity by the last-mentioned con nections. The initial meterbias may, of course. be adjusted by adjusting the position of tap I2along resistor I4.

One plate of condenser 40, which forms a part of the gauge head 80,shown in Figs. 2 and 3, is connected directly to the anodes of rectifier56, and the other plate thereof is directly grounded, in this casethrough the frame of the gauge head 80. The anodes of rectifier 58 arealso directly connected to the grounded terminal 19 and, for the reasonmentioned below, an additional adjustable ground connection 82 isprovided to variably determine the length of the conductor between suchanodes and ground.

Referring now to the gauge head 80, the preferred and illustratedembodiment comprises stationarily supported upper and lower framemembers 84 and 86. The lower condenser plate 40a, which may be formed ofsteel or equivalent material, comprises a thickened end portion 90, arelatively thin intermediate portion 92, and a somewhat thickerconnecting portion 94. The upper plate 401) is similarly constructed.These plates are rigidly secured to the lower frame member 86 by aplurality of studs 95 which pass through the bodies thereof and whichare insulated from at least one of such condenser plates. A spacer block98 of insulating material is interposed between the right-hand end orconnecting portions of the plates, and a similar piece of insulatingmaterial I00 overlies the upper plate. The lower plate 40a, whichdirectly overlies and is electrically continuous with the frame member86, so as to afford the above-mentioned direct ground connection, issuitably formed so as to tend to assume a slightly arched shape, whichcauses its left-hand end to normally rest upon the correspondingleft-hand supporting portion of the frame member 85. imparted to plate40a in various ways, for example, by surface grinding the upper surfacethereof, as will be understood. A gauge pin I02 is threaded into theplate portion 90 of the lower plate 40a and passes freely through anenlarged opening in the lower frame member 86.

In order to provide an adjustment of the normal spacing between theeffective plate portions of plates 40a and 40b, upper plate 40b issurmounted by a resilient springlike member I04 which is connectedthereto by studs 96, but is insulated therefrom. An adjusting screw I06bears against the elevated left-hand end of spring I04. As will beunderstood, if screw I06 is turned down, it lowers the left-hand end ofthe spring I04 and applies a pressure to the upper plate member 4% whichtends to lower its left-hand end portion and. reduce the spacing betweenthe opposed facesof the plate portions of the condenser plates. Thisadjustment determines the initial or normal capacity of the condenser40, as will be understood.

In use, the gauge head is stationarily disposed with respect to acooperating fixed workholder I08 which serves to stationarily supportthe illustrative workpiece W at a predetermined elevation with respectto the gauge pin I02. The adjustment of the parts is such that with aworkpiece W of desired dimensions, such workpiece, when introduced intothe holder I08, is engaged by pin I02 and elevates it from its normalposition by an amount slightly in excess of the maximum expectedvariation in workpiece sizes. This action establishes a normalcapacityvalue for condenser 40 which corresponds to Such tendency maybethe dimensions or the master-sample, as w'ill 'be appreciated. "ltwill "furtherhe appreciated that:

scale, the length of the lower plate 86 being :ap'

proximately two and one-half inches and the other-elements beingproportionately sized. As a fur ther example, the normal-spacing betweenthe plates may be of the order :of 'flve thou- 'sandths of aninch,-the-minimum-=and maxim-um spacings representing departurestherefrom equal "to the expected *variations in dimensions of theworkpieces which are t-o be gauged.

Considering now the operation of the sys'tem, it "will be =-appreciatedfrom previous description that the potential, with respect toground, orthe oscillator output terminal 54, pulsates at a frequency which isdetermined "by :the impedtimes of the oscillator and measuring networks,the amplitude of these pulsations"being adjustable by adjustment of the--'-condenser :62. It will sloe understood 'f-urther thatterminal 54corresponds to a position of substantially maximumiamplitu'de of whatappears to be a standing-wave established by these pulsations in theconductor 58. The just-mentioned standing wavesis :of substantiallysinusoidal form, as will be understood, intermediate portions whereof;

b'etweenithe peak and the node, are substantially linear. .Preferably,the system is adjusted so that throughout the expected operating range,the measuring circuit is subjected to voltage changes WhichJfall withinthis substantially linear portion of vthestanding wave. Consequently,inithetpracticewof the invention the length of conductor @58is-such'that the anodes of rectifier 56are electrically spacedfromterminall'54 by an amount suflicient to bring these anodes at an'intermediate point, on the standing wave, between. a peak anda nodethereof. This region may bein'the space between terminal 54 which is,as'hereinbef-ore :set forth, a peak point, and the first :or --asucceeding mode. :More particularly, a cconductor length which:establishes a spacing approximately =three-quarters of a quarter-wavelength ispreferred in manyicases. In 'other teases, :as discussed below,"and particularly with systems "embodying the hereinafter describedimprovements respecting linearity, meter locations which 'arefnearer thepeakare preferred. Similar comments'apply to the connection of the upperplate of condenser 40 with respect .to the terminal 54, which terminalis connected to the rectifier anodes immediately adjacent thereto. Thepotentials of the anode and condenser terminals-thus pulsate at thesourcefrequency "and at an amplitude determined by their positionbetween a peak and'a node of the aforesaid standing wave.

'It will further beappreciated that the ground connection 80 82 isspaced from the anodes by an amount 'sufiicient 'to'establish suchground connection in the region of a node of the standingwaverpreferablythe first'no'de which ='tollowsthc position" of the rectifier-condenserconnecti-on.

"current how 'in -the measuring "circuit, "as "a "7-5 conseqence o! arealternating zpotential applied to the "anode terminals, :is of icou-rserrectifie'd by rectifier .156 :and elevates Iterminal :51 :to .a valuewhich enables .it Ito overcome the :negative bias norm ally established:by =the :positionof 'tap' 'IiZ. 'iThe adjustmen-t oiithe circuitiissuchthat a workpiece of desired sizevestablishes an intermediatesubstantially zero :reading on :the meter, larger or smaller 7 samplesproducing acorresponding departures to one side or :the other of thecentral position, as -will :be understood.

It will further be understood 5 that variations in 'the -capacity ofcondenser '40, a -.:determined by 'thefsize 0f '-the workpieces, by:.virtue oflitscoupling to the oscillator r-network alter the irequencyi of the oscillator, thereby changing the Wave length of thestandingwave produced in conductor 53 and consequently "the physicalfloca'tion of the nodes :and peaks along this :con-

ductor :58. lsince the'oscillajtor network I0 al ways -acts to maintain:terminal 54 at ca :peak

point, the node points will move closer-together cation of the anodes"of rectifier 56 remain 'at' a fixed physical location on the-conductori5'ii. As the frequency or :wave 5 length of the standingwaveimpressed on conductor 58 is variedi'by the capacitor or condenser 40,the point onithe voltage wave at which "the anodes: of :rec'tifier '56are connected will have a' higher -or lower amplitude voltage changeas'th'e relative positions or the physically fixe'd location o'f the-connection of the anodes of rectifier 56tothe conductor '58 and thestanding wave are changed, either toward or away from the peak. Thisamplitude change is reflected in'the amplitude of the voltage appliedto, and the current passed by, rectifier 56. The current-passed by therectifier is measured by the microammeter "63; The microammeter 63,therefore, by itsindica-' tionof the changed current flow, is responsiveto the wave length of the standing wave, although it is preferablycalibrated not in amperes or meterswave length, but in fractionsof aninch above and below a zero reading which is obtained'from a workpieceofthe desired size.

It Will -beappreciated-thatthe sensitivlty of -themeasuring circuit isdirectly proportional to the source frequency. A three-meter wave lengthcan conveniently-handle changes inphysical "di mensionsof the order of.0001". In the event it is desired to 'measure physical changes of theorder of one or 'more'millionths ofan inch, itis desirable to use 'awavelength of one-half meter or less. Oscillators'utilizing tubes of theabovedescribed' type do not in general operate well at Inthe-originalanalysis of the beforementioned circuits it was believedthatthe variation-in *amplitude change of the standing wave indicatedby-themeter' fl was"due primari'ly to the"change f in wave length of the-standing wave-as deter- 7, mined by the condenser 40. Subsequentanalysis and more complete laboratory testing now indicate that a bettertheory of operation is that the variation in the amplitude changes, asindicated by the meter 63, are not only caused by the change in lengthof the standing wave but furthermore are influenced by a change inamplitude of the impressed standing wave. That there should be changesin the amplitude of the impressed standing wave after analysis seemsapparent when reference is had to the usual resonating amplitudecharacteristic curve as is shown in Fig. 5. In alternating currentcircuits as the length of the transmission line supplied from analternating current source, in this case the oscillating network I0,approaches a node point the line approaches what is known as aresonating condition and the amplitude of the impressed alternatingvoltage will rise substantially above the amplitude which appears underconditions away from resonance in the manner illustrated.

The capacityrelationship of a condenser of the type shown and describedis qualitatively shown in Fig. 4 and is in accord with the well-knowninverse ratio relation of the capacity of a condenser vs. spacing of thecondenser plate. Since the frequency of the oscillator network I willvary inversely as the change in capacity of the controlling condenser40, the frequency of the generated voltage cycle will varyproportionally to and in the opposite direction tothe capacity change.

The normal spacing of the plates 40a. and 40b of the condenser 40 with aworkpiece W of the desired dimension is that indicated as N in Fig. 4,and, the frequency of the oscillator network ID will be of a valueindicated as in. With a workpiece of a dimension which is undersizedsubstantially the maximum amount expected, the spacing of the condenserplates will be that indicated at U and the corresponding frequency ofthe network will be in. Likewise, an oversized workpiece of the maximumamount expected will result in a plate spacing O with the correspondingfrequency f0 of the network I 0. The changes in linear distance betweenthe plates 40a and 401) from N to U and N to O are equal, since normallyworkpieces will tend to be oversize and undersize equal amounts. It willbe noted, however, that the change in frequency from in to fu issubstantially less than that from in to f0.

Now referring to Fig. 5, wherein'curves a, b, c

and d represent the relationships of voltage magnitude plotted againstfrequency for various values of Q in the standing wave circuit, thefre-- quency values ju, In and f0 are indicated in relation to theresonating conditions of the conductor 58 with respect to the maximumvalues of the standing wave impressed thereon by the network II), thefrequency fu which corresponds most nearly to the resonating frequencyof the conductor 58 or in which the node point thereof most closelyapproaches the location of the ground connection 82 is indicated ashaving an amplitude of Au units and will of course be adjacent the highpoint of the'resonance curve. Since the resonating diagram is drawn withequal spacing of frequency along its horizontal axis, the frequency Inand f0 are spaced therealong in accordance with that determined by thecurve of Fig, 4. The intersection of vertical lines drawn upwardly fromthe points In and in with the resonance curve will determine theamplitude of the standing wave impressed on the conductor 58.

8V Now having determined the wave length and amplitude of the standingwaves, they may be drawn as shown in Fig. 6, in which the verticaldistance from the base line is indicative of the amplitude of the waveat any distance along the conductor 58 of Fig. 1 and 280 of Fig. '7 tothe node point as indicated by ground connection 82 or 242. If now theanodes of the rectifier 56 are connected to the point on the conductor58 as described before, the meter 63 will read the voltage X0, Xn, orXu, depending upon the size of the workpiece inserted in the holder I08,and with proper calibration of the meter, the dimension of the workpiecemay be indicated. Figure 6 also indicates diagrammatically with respectto the length of the standing wave the length of the conductors 58 and200 to show the somewhat initial dimensions thereof. It is to beunderstood, however, that the presence of the condensers 40, 60, 62 and246 will in some respects change the shape of the voltage waves due toachange in the scale of the abscissa caused by their presence. Forconvenience, the abscissa and ordinate scales have been made linear tobetter show the sine form of the voltage curves.

The circuit shown in Fig. 7 is utilized in the apparatus shown in Fig. 8and is similar in many respects to that shown in Fig. 1, however, itembodies certain improvements and additions thereover which will behereinafter specifically pointed out.

Referring to Fig. 8, numeral I represents generally a hopper for theworkpieces to be gauged or measured, which in this instance may becylindrical workpieces I22. A rotary member I24 within the hopper shellI26 is rotated by suitable means not shown and feeds the workpiece I22into the chute I28 which feeds these workpieces into the work holder I08of the gauge head 80'. After measurement, a solenoid operated ejectorI36 pushes the measured workpiece I22 into the discharge chute I34. Theworkpiece slides down this chute I34 and, depending upon the conditionof the gates I36 and I 38, will either slide completely through thechute I34 into the undersized bin I411, be diverted by the gate I36 intothe normal or acceptable bin I42 or be diverted by the gate I38 into theoversize bin I44. Immediately upon ejection of the measured workpiece, anew workpiece from the chute I28 will be positioned in the work holderI08 by a plunger I46 driven by the motor I32. to the gauge head 80except that an actuating lever I50 has been added so that an oversizeworkpiece instead of causing the plates 49a and 40b to be moved closertogether moves them apart and, conversely, an undersize piece causesthem to move closer together.

Referring to the circuit shown in Fig. 7, the entry of a workpiece I22into the work holder I08 will position the condenser plates 40a and 402)with respect to each other and adjust the length and amplitude of thestanding wave in the conductor 200 so that the voltage therealong at thepoint V will be proportional to the size of the workpiece I22 beingmeasured. If the magnitude of this voltage is within the desired rangeindicative of a workpiece falling within the proper tolerance, theproper bias will be applied to the grid of the valve 202 to permit apredetermined current flow to be passed therethrough which, due to thepotential drop across a resistor 204, will raise the bias voltage of thegrid of valve 206 to permit this valve to pass sufiicient current toactuate the relay 208 which controls the accepta- The gauge head issimilar ble-gate. I36 andIthe-Workpiece finds its way into the.acceptablev bin.l42. If the workpiece I22 is undersize, thevoltage atpoint V will be insufficient to' permitvalve 202 to raise the potentialofthegridof'valve 206 sufficiently to actuate the relay 288" and. theworkpiece will pass completely through the chute I341 to the undersizebin I40, whilea workpiece of oversize'dimension willraise thepotential'of the grid of valve 202 sufliciently to cause avalve 2H] aswell as valve206 to conduct suffi'cient toactuate the relay 2I2 toactuate the oversizegate I38 which it will be noted is anterior to thegate I36 so'that'it controls irrespective of the gate I36 and theworkpiece ends'up in the oversize bin I44.

It will at once be realized that the circuit of Fig. Tactsinstantaneously and it willtake an appreciable length of time for-theworkpiece to pass down the chute I34 beyond the gates I36 and I38. Inorder toprevent a change in position of'the adjusted gates I36 and/orI38. during this interval', the variable resistors 2I4 and 2I6associatedwith the cathodes of the valves 296'and 2I0, respectively, areadjusted so that, with the minimum or leakage current flow through thesevalves, the relays 208. and 2I2 when once closed will'remain closed butwhich current is of itself insufficient to close the relays 208 and 2I2when they are in. open.position. A valve 2IB becomes conductive at apredeterminedtime interval after the-valve206 actuatesthe relay 288,such a time being determined by a condenser 220' and the setting'of. thevariable resistor 222' as will be described more fully hereinafter andwhich interval is sufiicient for the workpiece to pass by the gates I36and I38. The -rendering of valve 2!!! conductive actuates a relay 224which opens the circuitthroughthe coils of the relays 208 and 2| 2whereby they: are completely de-energized. Im-

mediately-upon movement of the relay 208 toits de-energized position,the condenser 220 is shorted' out and the valve 2I8 renderedsubstantially nonconductive to de-energize relay 224 closing contacts athereof to again place the gate system in condition for reoperation bythe valve 248.

More specifically, the networks illustrated in Fig; 7 comprise a supplytransformer 20 having its primary winding energized from a suitablesource of alternating current supply such as conductors 226 and 228under control of the switch 22 and a voltage regulating transformer 23!]which acts to smooth out the voltage fluctuations of" the supply line sothat the primary winding of the transformer 20' is supplied with morenear- Iy-substantial constant E; M. F. Such a transformer-23B is readilyobtainable in the open marketrunderthe trade name Sola. The mainsecondarywin'ding of the transformer 20 has its end terminals connectedto the anodes of a rectifier valve 232 of the type commonly known as6X5. The rectifier'valve232 as well as valves 2'02, 285, 219i and 218have filament heaters which are supplied with energy from the auxiliarysecondary winding of the transformer 20 as indicated by the charactersat; y. The cathode'of therectifier valve 232 is connected to supply 3+or positive D; C; voltage to a bus 234 through a radio frequencychoke'236 having by-pass condensers 238 and. 240 connected between therespective end of the choke 236 and ground bus 242. The center tap 2-18:of the main secondary winding ofthe transformer 20 is directly connectedto ground 242' which is a negative D. C; or B power supply-busThegcenter terminal 5!! of tank coil 44 connected to: the B+ bus: 234.One end terminal; of the. tank coil 44 is: connected directly with aworkpiece-changein size of'.0001"'.

and closely to theanode of'anoscillator-valve 244; the grid of which isconnected through-a condenser 41 to the opposite end of the tank coil 44and also through a resistor 48 to B- bu 242 which may be the metalchassis upon which the instrumentalities are mounted. The cathode of thevalve 244-is connected to. ground 242 whereby B potential is suppliedthereto.-

The anode of, valve 244 is connected through a pair of seriesconnectedcondensers and 62 to the conductor 2illlwhich is of.apredetermined length-with its far. end connected to ground 242. i heconductor 2% corresponds in many respects toconductor seer Fig. 1 andwhen considered in connection with; the. values of the condenser 4.9, ofthe gauge head and the condenser 25% is of a length equal toapproximately, onequarter of the wave length of the-standingwaveimpressed. thereon by the oscillating network comprising the'valve244-and tank coil 44.

As inthe system-of Fig. 1, the potential 01? a standing wave on the.conductor 200 Y is measured by; an electric'valve24B having a pairotanodes which are connectedtogether andtotheconductor 2IlIl-at thedesired location V. Thevalve 248 has a right-hand and a left-handcathode, the right-hand-one ofwhichis connected through a variableresistance 250 and a microammeter 2-52 to: ground 242. The left-hand.one of the cathodes of the valve 248 issconnected to ground 242 througha resistor'254whichmay be variable for purposes of calibration ifdesired. The heater filament for the valve 248 isconnected as indicatedby the characters as, y to thetrans former 20. A pair of condensers 256,258 are connected in series between the two cathodes of, the valve- 248-and the condenser common terminals are connected to ground 242..

The variable condenser 246-primarily controls the Q of the standingwavecircuit and isconrnected to the conductor 200 adjacent the con-'-nection thereto of the anodes ofthe valve 248 and has its other terminalconnectedto ground 242-. Connected at thissame junction V to the line,2001s one-end of the concentric center lead 269 of a shielded conductor2-6-I, the other end of the lead 266 is connected to one plate of thecondenser 49 of gauge head8ll. The other plate of the condenser 40 ofgauge head 8!! is connected to the shield covering of the conductor 26I,which covering is connected to ground 242 at its end" adjacent theconnection V.

When using a wave length of 10 meters, a

conductor 26I of an approximate length of two feet is satisfactory for afull scale deflection of the meter 252 with a workpiece size change of.002" with a one-to-one ratio of the lever I150. Under such a condition,the value of condenser 50' and normal value of condensers 62' and' 245is .000012 M. M; F.', while the range in values of'the condenser 40 is.000045 to .0'0009'5 M. M. F. The length of conductor 2% from the anodeof the valve 244 to point V'is 1 including the condensers 60 and 62,while'the length of the conductor 21m from the point V to the ground 242is 22 By experiment, it has been found that by decreasing the length ofthe cable 261 to 12" the sensitivity f the instrument has been increasedto a point where a change in .0002

in size of the workpiece will give a full scale deflection. A furtherdecrease in length to 6" of the cable 26I will double thesensitivity andresult in a full scale change in the meter 252 While sensitivityapparently may be controlled'byvary the relay 20a to ground 242. ,everthe relay 208 is de-energized, the potential ing the length of the cable26I, it is preferred to change sensitivity by adjusting the condensers62 and 246 and by changing the fulcrum point I! of the lever I50, aswill be more fully described in connection with the more normal means ofadjusting the instrument.

The segregating network generally designated 262 comprises the electricvalves 202, 206, 2I0

and 2I8, the anodes of which are connected through current limitingresistors 264 to the B+ bus 234 by which they are supplied with apositive potential with respect to ground 242. The valve 202 may betermed the undersized valve since for any of the chute gates to open,the valve 202 must conduct suflicient current to raise the potential ofthe valve 206 a predetermined amount. The grid of this valve 202 isconnected through a resistor 266 to the left-hand cathode of the valve248. The potential of the grid of valve 202 above ground is controlledby the voltage drop across the resistor 254. The cathode of the valve202 is connected through the resistor 204 to ground 242 and to the gridof the valves 206 and 2I0 so that the potential above ground of thegrids of the valves 206 and 2I0 will be the potential drop across theresistor 204. It will be obvious that when minimum or leakage current isbeing passed by the valve 202, there will be a minimum voltage dropacross the resistor 204 and the grids of the valves 206 and 2I0 will beat their minimum potential above ground 242.

The cathode of the valve 206 is connected through the resistor 2I4 toone terminal of the energizing coil of relay 208, the other terminal ofwhich is connected through normally closed contacts a of the relay 224to ground 242. Similarly, the cathode of the valve 2I0 is connectedthrough the resistor 2 I 6 and the energizing winding of the relay 2I2and normally closed contacts b of the relay 224 to ground 242. It willbe appreciated that a drain current will flow through the valves 206 and2I0 and which current flowing through the resistors 2I4 and H6,respectively, will raise the potential of the oathode of the respectivevalves 206 and 2I0 above the potential of the ground 242. This drop, byvarying the value of the resistors, may be adjusted and, for the usualtype of high vacuum valve which may be used, will bring the potential ofthe cathode above that of the respective grid so that the grid isnegatively biased with respect to the cathode to normally maintain therelays 208 and 2I2 unactuated.

' The cathode of the valve 2I8 is connected to 'one terminal of theenergizing winding of the '2I0 and 2I8. The grid of the valve 2I0 isalso connected through the resistor 262 to ground 242 and also connectedby way of a conductor 266 through the normally closed contacts a ofTherefore, whenof the grid of the valve 2I8 with respect to its cathodewill be such as to maintain the valve 2 I 8 at its minimum conductingconditions which is insufficient to actuate the relay 224. As statedhereinbefore, any workpieceswhich are not diverted from the chute byeither the acceptable gate 'I36 or the oversized gate I38 will ofnecessity-be carried into the undersized bin I40.

tion 366.

The gate 136 is controlled by means of a solenoid 268 while theoversized gate I38 which is located along the chute I34 closer to thegauge head 00' than the gate I36, is controlled by means of the solenoid270. One terminal of each of the solenoids 268 and 210 is connected toone end of the secondary winding of a power supply transformer 212having its primary windings supplied with energy from the conductors 226and 228. The other end of winding of the solenoid 268 is connectedthrough the normally open contacts b of the relay 208 to the terminal ofthe transformer 212. The other end of the energizing winding of thesolenoid 210 is likewise connected through the normally open contacts bof the relay 212 to the transformer 212. If desired; indicating lamps280 and 282 may be connected in parallel around the energizing windingsfor the solenoids 263 and 230-, respectively, so that a'visualindication may be had as to the operation of these two solenoids and ofthe acceptable and oversized gates I36 and I38.

Under certain operating conditions, it may be desired to eliminate thevalve 202 and toconnect the left-hand cathode of :the valve 248 directlyto the grids of the valves 206 and 210. This is possible since the valve202 acts as a relay.

Referring to Fig. 9 in which another form of gauge head construction isshown, the numeral 330 designates generally a housing member hav ing atop wall 332, a front wall 334, a rear wall 336, and side walls 330 and346 and a chambered interior 342 which opens downwardly and outwardly ofthe casing 330, and is closed by a second casing 344 having a wall 346with an upwardly extending peripheral flange 348. Screws 350 secure thecasing 344 against the open lower side of the casing 330 and a gasket352 is compressed between the adjacent portions of' the casing 330 and.the flange 348 whereby the interior chamber 342 of the casing 336 issubstantially sealed. A platelike supporting member 334 is held at oneend by a screw 356 against a shoulder 358 of the end wall 336 and at theother end by being clamped intermediate the lower edge portion of thewall 334 and the top edge adjacent portion of the flange 348.

The lower condenser plate 360 seats against this supporting bar 354 andis in electrical contact therewith. The lower condenser plate 360comprises more specifically a rigidly secured end portion 362 and amovable end portion 364 hingedly secured to the rigid portion 362' bymeans of an integral thin section bridging por- Preferably, the lowercondenser plate 360 is fabricated from a single block of metal havingthe cross section required for the movable portion 364 and which has aportion machined away to provide the rigid portion 362 while it has anintermediate portion thereof machined much further away leaving only therelatively thin flexible bridging portion 365. The fixed condenser plate368 comprises generally a rectangular block of metal of the sameover-all length as is the lower condenser plate 360. The portion of theupper plate 368, which is located above the fixed portion 362 of thelower condenser plate 360, is spaced therefrom by means of a block ofinsulating material 310 which may be fiber or other similar material. Ifdesired, shims 37'! may also be used. The block 310, the fixed portion362, and the fixed condenser p1atej368 have spaced aligned holes throughwhich securing screws 312 and 314 extend. The screw 312, which isclosest to the'end wall 336, is-screiw threaded acetates '13 its-lower?end: portion into the; support 354'. Tihemther screw '3] 4" extendsthrough a clearance hole: in. thesupport 3 54' and has at its lower endportion a: nut. 316' for' adjusting the tension impartediby this screw.Preferably, the screw 312 is tightcned to' rigidly secure the rear endportion. of: the fixed condenser plate .368 relative to the support 354=and the nut.3-1 is-screw threaded on:- the: screw 3M topivot the fixedmember' 3% about the screw 31 21" until the. proper nonparallelrelationship is' provided between the lower face of this member 368andthe upper face of: the movable portion of the lower condenser plate350; when; the lower surface. of the portion 354 is in; engagement: withthe. supporting member a 3-54: The: supporting member 354' also has anaperture- 318': therethrough in which a pin 38!) freely extends. Theupper end portion of the pin 38! is received within an aperture 382 inthe lower faceof the movable portion 354 of the lower condenser member360. The lower endof this pin 380- rests; against the upper surface-oithevlever. arm I50. whichis loeatedabove the wall 346 and. within thecavity formed by the uption of'the. f'eel'er 294 engages the lowersurface ofthe. lever atlthe. opposite end from that engaged by the. pin38.0. whereby movement there.- of .will. rotatethe. lever I50 about. itsfulcrum I51; 'Thewall1336. above the feeler 294 has an aperture whichreceives a helicalcoil. compression spring 3926 which is held undercontrolled compression by means of 'a screw threaded plug 398 wherebythe lever. [511 is continually held in. engagement with. the upperendlportion of the feeler 29.4.. The end'wall 334lhas. spacedscrew.threaded apertures for reception of screws. for securing the gaugeheadcasing 330 to a. gauge head supporting base 300. The lower condenserplate 369. is inel'ectri'cal connection with the support 354' and'thecasing 330'. The upper condenser plate 358 is in- 'sulated" from thescrews..312 and 314' by suitable means such as an insulated strip 400'and having the apertures. t'herethroug-h substantially of larger.diameter than that ofthescrews 312. and 31.4. Theplate 3 88 iselectrically connectedby. a

lead" 6'01 tot the center contact 402 ofa terminal member 384- mayextend in the reversedirection.

from-the supports 390" and 392- and the supports 38B and 388 may bemoved downwardly along the lever" I50 so that a second or a one-to-oneratio maybe provided between the feeler 294 and the pin.380. It has beenfound from experience that the utilization of either one of these twolever ratiosyin connection with the condenser plates 360* and 368: willhandlesubstantiallyall ranges ofmeasurementsto bemade by the gauge head.

iltwill be obvious,\offcnurserthatzother ratios on thell'ever" I50maybe:established:as desired. It is to" be further 1 understood; that:theagauge: head ofiFigs; 9-andl0 maybesubstitutedlfor the gauge headtfior 80.3.

Figure-ll showszeanmodifi'ed form-10f: segregator networkrini whichdiscontinuous: control. typetgas filled valves: 206a and. 2I0a:-are:usediimplacemf the: valves": 206 and 2 In of Fig; 7;;valves-2262 and 218: being omitted in this arrangements The en'-ergizing' winding; for the relay 208: connected between the B+- bus234,: and thez-anode of valve 206a; through;- contacts a: of; a: switch22 5.-=. Like.- wise, the energizing, winding; for the. relay 212: isconnectedfbetween the.=bus- 234- and the anodeeof the-valve 2 Illathrough contacts I) of the switch 225., The cathodes of. the-valves206a. and. 21011 are :connectedto. intermediate points of resistors Viandv V2 having their end-terminalsconnected between bus1234-and ground24250 that the: oath.- ode potential thereoflw-ill normally bemaintainedat a greater positive potential. than that of the grids thereof, wherebythe valves ZUlBmandZ-Ma will; not? conduct. until. the. potential. ofthe. lefthand cathode of the-valve: 2 M}v is raised: suificiently bytheworkpiece'to' actuate-either or both. gates I36 and: I38; In this.instance,.the motor I32 mechanically actuatesthe switch 225- through cam22: after the work-piece hashadtime to'pass the gates. and I38. torendersthevalves 205a and 249a again under control of the-valve 248.

It believed that the remainder of the: details of constructionmay bestbe understood. by-reference to the descriptionof theoperation of thesystem.. Upon closure ofthevswitchzn',thetranse former 2 I!- isenergized. supplying, heating. current tothe filamentof the valves;202,. 2E6 2H},.2-.l8, 232, 244'and 248. After these valvesihave warmedup. sufiiciently so: that. they are inanoperating condition, thesystemwill function.. The. valve 244 willoscillate in the usual fashionsince this portion of the circuit is broadly similar to the well. knownHartley oscillator. Thefrequency of oscillation of the valve 244is-determined partially by the value of the condenser 41 and to. a greatextent by the. valuesof the condenser 30 of the gauge head 88' andthe-condenser =60, 62 and-.246. Astanding wave will beset up in theconductor 280. Since the grounded end portion of conductor. 296 islocated substantially one quarter of a wave. l'engthfrom the anodeof.valve 244-,- the conductor 2M willlbe at resonance and the amplitudethereof will be. maximum for. the value. of condensers fifl and.62.

In the discussion. of the theory of operation of the form shown in Fig.1., reference Wasmade to. the changing voltage which was picked up. bythe rectifier tube 55 at the point X. By reason of further analysis anddevelopment of the system shown in Fig. 1, it wasdecided that animprove.- ment in' the operation could be had if. the voltage instead ofbeing picked off atthe point'Xwas picked off at the point V, and.therefore the point V of Fig. 7 has been moved along the'longitudinalaxis of Fig. 6 to the point generally designated V. At this time it isdesired to make it clear that under certain conditions of operation itmay be desired to move thepoint V' further toward the crest ofantinodepoint of. the. standingv wave which occurs substantially at theanode of the valve 248. Under certain otherconditionsit mayIce-desirable to actually connect the point V'to the-anodeof the valve244" in. which. case. it appears that the primary change: in voltage isamplitude-change:

Let= us now assume that the instrumentalities' of Fig. 7 are to beadjusted to read at full scale deflection .0002". The center or zeropoint of the scale will be the normal reading, say, for example,1.000000". Full scale deflection to the left or to will be 1.000100" andfull scale to the right or to U will be 0.999900". A block of thedimension 0.999900" is inserted in the work head I08 against the anvil290 which is positioned by means of screw adjustment 292 so that thefeeler tip 294 will rest against the opposite surface of the test block.The relative spacing between the gauge head 80 and holder I08 isadjusted by bodily moving the gauge head 80' upwardly or downwardly withrespect to the anvil 290 until the pointer on the meter 252 reads U; thegauge head being movable by loosening holding screws 206, one only beingshown, which extend through slots 298 in the gauge head supporting base300 and screw threaded into a supporting plate 302 rigid with thesupporting member for the anvil 290. If desired, a screw threadedadjustment between plate 302 and base 300 may be provided.

In this manner the distance between the plates 40a and 40b is adjustedto bring the frequency of the standing wave to approximately the valuefu' (Fig. 4) and an amplitude of Au (Fig. 5). Next a block of the normalor 1.000000 dimension is placed inthe work holder I08, and the trimmercondenser 62 is adjusted until the meter reads N or at midpoint on themeter scale. This adjusts the point AN (Fig. 5). Since an adjustment ofcondenser 62 will, to some extent, change the amplitude of the standingwave at the frequency in (Fig. 5), it will again be necessary to replacethe 0.999900 block in the holder I08 and, if necessary, readjust thesetting between the plate 302 and base 300 and to recheck the setting ofthe condenser 02 with the 1.000000 block. Now having reached anapproximate adjustment for the U to N range of the meter or theundersize workpiece range, a block of a dimension equal to 1.000100 isplaced in the holder I08 and the trimmer condenser 245 is adjusted tovary the Q of the circuit until the meter needle is pointing to the fullscale reading to the right or point 0-, thereby adjusting the point A0.The block 1.000000 is then again re-used and condenser 62 readjusted, ifnecessary, as described before, for rechecking the point AN, since achange in the value of the condenser 246, while changing the amplitudeof point A0, greatly may also change the amplitude of point AN, althoughto a lesser degree. The 1.000100 block is again used and the condenser246 readjusted as before. When the approximate adjustments for the N to0' range of the meter or oversize workpiece range have been obtained,the blocks 0.999900, 1.000000, and 1.000100 are again placed in theholder I08 and readjusted as above, if necessary, until the accurateadjustment of the condensers 62 and 240 and of the base 300 with respect to the plate 302 is obtained. I

It will now be apparent with the adjustments just made that therelationships shown in Fig. 6 are present when the connection of theanodes of the valve 248 are at the location V.

Since the curve as represented in Fig. 4 is of generally opposite shapeto the curve of Fig. 5, the point V may be located within limits atvarious locations along the conductor 200 and by an adjustment, asdescribed above, substantial linearity may be imparted to the readingsof the meter 252. Such linearity makes it easier for an operatorto checkworkpieces and reduces strain when such a gauge is utilized to measurethe absolute dimension of workpieces. The relative effect of changes inthe readings of the meter 252 with respect to amplitude changes of thestanding wave in the conductor 200 may further be adjusted by theresistor 250. This enables the operator to further combine the curves ofFigs. 4 and 5 in the interest of linearity.

To enlarge the scope of the above instrument, the relative positions ofthe gauge head and holder I08 can be varied in any desired manner, as bythe adjusting screw 292. For example, with a normal spacing for use withworkpieces of 1.000000", the holder I08 is at a fixed position withrespect to the head 30. If pieces of 2.000000" are to be measured withthe same scale adjustment of the meter 252, it is merely necessary tomove the anvil 290 outwardly from the gauge head an additional 1.000000"and the instrument will measure from 2.000100 to 1.999900".

Within limits, the adjusting screws 292 and 290 can be used to calibratethe meter 252 to measure various dimensions over a full scale deflection. If it is desired to operate outside of that range, such maybeaccomplished by changing the fulcrum point I5I to provide differentmovements of the condenser plate 40a with re spect to dimension of theworkpiece I22.

So far described, the instrumentalities of Fig. 7 merely act'to give avisual indication of the size of the measured workpieces. Since inproduction measuring it is desirable to visually spot check workpiecesand desirable to accurately check and sort completely all workpieces ofa given variety, an automatic segregator. is also operated by the valve248 as follows: As the voltage at point V and the conductor 200fluctuates, current of a similar fluctuation will flow from the point Vthrough the left-hand anode of the valve 248 and through the resistor254 to the ground 242. Increase and decrease of thiscurrent flow throughthe resistor 254 will raise and lower the potential of the left-handcathode of the valve 248 with respect to the ground 242 and at the sametime will raise and lower the bias potential on the grid of the valve202. The change in bias on the grid of the valve 202 will regulate thecurrent flow through this valve and through the resistor 204 to theground 242, whereby the cathode of the valve 202 will also change inpotential with respect to ground 242. The grids of the valves 206 and 2!are directly connected to the cathode of the valve 202 and therefore asthe current flow through the valve 202 changes, so also will the bias onthe grids of the valves 206 and 2I0. At potentials of the point V belowa predetermined value with respect to the ground 242, the grid of thevalve 202 will not be made sufiiciently positive to permit suflicientflow through the valve 202 to raise the grids of either of the valves205 or 2I0 to bring these valves into a conducting condition. This lowvoltage corresponds to all voltages below voltage VII of Fig. 6 or anyother voltage indicative of the minimum size acceptable piece as may bedetermined further by adjustment of the variable resistance 2 I4.

When workpieces of a dimension which is above the minimum acceptabledimension are passed through the work holder I08, the grid of the valve206 will be made suficiently positive to permit enough flow of currentthrough the valve 206 and resistor 2I4 to actuate the relay 208.Actuation of the relay 208 closes the consize work bin I40." When nowthe size of the workpiece I22 in the work holder I08 is above theacceptable size, the resistance 2I6 is so adjusted that the potential ofthe grid of the valve 2 I is suflicient to cause this valve 2 I 8 toconduct enough current through the relay 2 I2 to actuate the same andclose the contacts b thereof. Closure of the contacts 12 energizes thesolenoid 210, which controls the oversize gate I38 and which therebydeflects the oversized workpiece into the oversized bin I44; it beingunderstood from the foregoing description that the oversized gate I38 islocated intermediate the acceptable gate I36 and the work holder I08 sothat even though the valve 206 is conducting at the same time that thevalve 2I0 conducts and causes its relay 208 to operate the gate I36, theworkpiece is diverted by the oversized gate I38 prior to reaching theacceptable gate I36. It may now be seen that the'valve 248 not onlycontrolls a visual device Whichindicates the size of the workpieceI22'then in the work holder I08, but also actuates a series of relayscontrolling gates whereby the workpieces are segregated into theundersize, acceptable, or oversized work bin.

As stated before, the actuation of the measuring circuit issubstantially instantaneous with the positioning of the gauge head 80',andtherefore a1 suificient time delay must be provided for the gates sothat, when once set, they will not move to another position until suchtime as they have deflected the workpiece into the proper bin. Suchdelay is effected by adjusting the relays 208 and 2I2 so that, when onceactuated, they will remain in their actuated position with the minimumleakage current flow through the valves 206 and 2I0 respectively. Sincethe relays 208 and 2 I2 are so adjusted, means must be provided forresetting of the relays. This resetting occurs at the expiration of apredetermined time interval subsequent to measurement of'the piece bythe gauge head 88, which time interval is sufficient for the proper oneof the gates to deflect the workpiece into the proper bin. This isaccomplished by means of the valve 2 I8.

The gridof the valve 2I8, it will be noted, is directly connected to the13-}- bus 234 through the variable resistor 222 and is also directlyconnected through the resistor 262 to the B- or' ground 242'. The gridof the valve 2 I8 therefore, from the above connections, will assumeapotential intermediate the potential of the 13-}- bus 234and the B-ground 242, which valve is dependent upon the relative values of theresistors 222 and 262. The conductor 266 by-passes the resistor 262 andis under control of the contacts a of the relay 208. With the relay 208de-energized, the contacts a thereof are closed, completely shorting theresistor 262 and placing the grid of the valve 2I8 at the same potentialas the ground 242; the

resistor 222, is then passing suflicient current toabsorb the completevoltage potential which exists between the bus 234 and the ground 242.When, however, the relay 208 is energized and the contacts a thereof areopened, the potential of the grid of the valve 2 I8 increases in apositive direction with respectto the cathode of this valve,

18 permitting this valve to pass suflicient current to actuate the relay224. It will be noted, however, that a condenser 220 is connectedbetween the grid and cathode of the valve 2I8 so that the relativepotentials of the grid and cathode ofthe valve 2 I8 are not instantlychanged as soon as the contacts a 01 the relay 208 are opened. Since thecondenser 220 takes an appreciable length of time for charging, whichcharging is necessary before the grid potential may be brought abovethat of the cathode potential of the valve 2 I 8, this charging time ofcondenser 220 is used to provide the time delay necessary tobe sure thatthe gates have diverted the measured workpiece into the proper bin.

As soon as the condenser 220 has charged the predetermined amount andthe valve 2I8,con-' ducts to actuate the relay 224, the contactsa and 1)thereof open, completely breaking the circuits through the energizingwindings of the relays 288 and 2 I2 whereby these relays 208 and 2I2move to their de-energized position, closing the contacts a of the relay208 and opening the contacts I) of each of the relays 208 and 2I2.Opening of the contacts b of the relays 206 and 2I2 de-energizes thesolenoids 268 and 210 of the acceptable and oversized gates I36 and I38,re-' spectively, permitting these gates to swing to their open position,thereby opening the chute I34 directly to the undersized bin. Closure ofthe contacts a of the relay 208 again re-establishes a short circuitabout the resistor 262 and substantially instantaneously discharging thecondenser 22 0, whereby the positive bias on the grid of the valve 2I8is reduced so that the currentflow therethrough is insufiicient tomaintain the relay 224 in an operated position. Contacts a and b thereofthen close, thereby placing-the relays 208 and 2I2 under control oftheir respective actuating controlling valves 206 and 2 I0. Discharge ofthe condenser 220 again .places it in readiness for another delayholding action of the firing of the valve 2I8 which controls the gates268 and-210 as above described' It quite often happens that an operatorwatching the meter 252 wishes to ascertain whether the varioussegregating circuits are operating correctly, and for this purpose theindicating lights 280 and 282 are provided. If the work is undersize,neither of the lights 280 nor 282 will be energized; if the work isacceptable, the light- 280, in parallel with the solenoid 268, will beenergized; and if the work is oversize, both the light 288- and thelight 282 will be energized, indicating to the operator that the work isbeing placed in the oversize bin.

It will be appreciated that proportionings of the various electricalelements in the circuits may be varied within relatively wide limits,illustrative ratings being indicated in the drawing.

It will alsobe appreciated from the foregoing that the present inventionprovides an extremely simple and effective method and apparatus formeasuring minute variations in the characteristics of a workpiece. Inaccordance with the statute,-a preferred use of the invention which isfor measuring the physical or lineal dimensions of a workpiece has beendisclosed in detail. However, this is only one use to which the systemcould be placed. It is believedthat the basic concept which is the useof an impedance element 46 for varying the output frequency of theoscillator circuit I0 is very much broader than the specific embodimentof a condenser having, one of its plates moved by the physical dimensionof a workpiece in that, generically, any impedance aces-54s;

19' element could-be substituted:thereforiwhichwould vary the outputfrequencyof the-oscillator; such as an inductance coil connectedintcombination for receiving a workpiecebartwhich changes the impedanceof'the inductance coil which in: turn would change the output "frequencyof. the oscillator Hi and for which the output frequency or lengthand/or'amplitude of thewstanding. wave in the conductor 58 .Wouldbemeasured by a H111 croammeter 63. Other similar arrangements could bemade I in' connection with: hardness changes which are usually tested bythe'amount thesurfaceof'a piece will be depressed under a predeterminedforce per unit area; It will fur-i ther be understood: thatvarious'modifications in the form," number-andarrangement of: parts maybe -made without departing from thespirit and scope of the invention.-

What is claimed is:

1. In an electrical'measuring systemtfor deter= mining a'characteristicof a workpiece, thelcom-a bination of "an oscillatory source havingoutput terminals, a measuring-network .coupled-ztosaid terminals and ofan electrical-:length such that'za reflected wave is produced. :therein.to: provide a standing Wave in said measuring'network, a measuringinstrument connected in said measuring network at a fixed location andresponsive to the 'am' plitude ofpulsations in said measuring network ata predetermined point, said measuring rnetwork being'tuned totheneighborhood. of :resonance to th'e frequency of said source, animpedance ele-V ment variably controllahle'hy' saidcharacteristic, andmeans coupling said elementtc said system so that changes inthe valuethereof alter the position ofsaid standing wave in saidmreasuringnetwork relative to said: predetermined point and thereby vary theamplitude oi'thepulsationsrapplied to said measuringlinstrument '2. The"systemofw JcIaim fl wherein said im.-. pedance-meansvariably determinesthe frequency of said source;

3. The systemxof claim l wherein :said'. im@- pedance elementis'coupled. to thecsource by a conductor of such a length that theelectrical characteristicsfiof: said impedance element. and semconductor are substantially those of a con ductorzhaving a length equalto:a multiple ofra quarter-wave length of saidsource.

4.-.In an electrical measuring system for measuring the size of .aworkpiece, network means includinglan electriclvalve for generating anoscile letting-voltage, a network .connectedlto said firstnamed network;and l operative to receive the;voltage" wave thererrom,. said last-namednetwork being of such electrical characteristics relative to thestrequencyof the oscillating voltage impressed thereon that reflectedvoltage waves areset up in said. last-named network to provide astanding voltage wavegcapacitance means responsive to the size: of theworkpiece for changing the frequencyofsaid oscillating voltage withinthe range which will vcontinue'to produce reflected voltage waves insaid last-named network, and means responsive to theresulting wave forindicating the size of the workpiece.

5. 'An electric: segregating, system comprising an -electrical vnetwork,means for impressing a standing voltage wave in said :network, meansresponsive to the magnitude of a characteristic ofaworkpiece'fordeterminingthe length of said wave; an electric valve having an anodeand a cathode, means connecting said anode tosaid network'whereby it isresponsive to changes in amplitude of said voltage wave, a resistanceelement connected between said cathode and the nodal potential-of saidvoltage waverwhereby the.

potential. .of said cathode is I proportional :to? the magnitude of saidvoltagewave atithe pointiz'of' connectionof said anode to said'networkja pair of control valves eachhaving. a pairiof'main elecetrodes and a controlelectrode, each said pairmf valves being operable"to pass current between -its said main electrodestin response to the*biasof said control *electrode'relative to onelofl its said mainelectrodes, circuit means for'biasing said control electrodesproportionally to the change' in potentialof said cathode; electricalcontrol apparatus .individualtto each of saidipairof valves; meansadjusting the ratio :of cathode voltage to control electrode voltage foreach 'of 'saids con trol electrodeswhereby' one :of said.- pair ofvalves acts to actuate. its: respective control ':apparatus atia lesservalue'of. said cathode voltage thantthe value of said cathode voltagefor th'e other :of said pair of valves to actuate its respectivercontrolapparatus :wherehy one of said control" apparatus is actuated-inresponse to a workpiecevhaving a larger "magnitude of' saidcharacteristic and whereby the other of saidacontro'l' apparatus :isactuated 'inuresponse'to a workpiece havingeta lesser magnitude of saidcharacteristic;- and sage regating apparatus controlled by 'said controlapparatus for segregating said workpiece in accord ance with'themagnitudes'of said characteristic;

6. In an electrical network foridetermininge the characteristics of 'aworkpiece, 'an="electrical "net-e work forhgenerating an oscillatingpotential" atza frequency not less: than tenzmillionrcycleeper secondand including annelectric:valve havingan anode and a cathode,an.electricalrnetwork havingone-end. connected to said. anode and' of"an electrical. length: not/less thanione quarter of the length. .of"the. electrical 1' wave produced by said generating network; avariable-impedance: ele-.- ment having a pair of terminals,meansconnect-z ingrone ofsaid' terminals to an intermediate point insaid second named network, means connecting the. other end 'of'isaidconductor. to said cathode, and potential measuring means connected to afirst point in said second'named networkandto said cathode for measuringthe potential therebetween;

7; In an electrical network 'for determining the characteristic of aworkpiece;xanelectric valve having an anode'anda' cathode and a gridsaidgrid. being arranged to continuously control the conductivity betweensaid anode and said cathode in accordance with aoias potential appearingbe-- tween saidgrid and said cathodepa'pair:oftermia nals adapted to besupplied with. a sourceofelectricalxpotential, a firstelectricallcircuit connected between said anode and saidcathodeincluding inductance and capacitance tuned to resonate. at afrequency of not less than 10 million cycles per second, a secondelectrical circuit connecting one of said terminals .through'at least aportion of said inductance to said anode and connecting-a second of saidterminals tosaid cathode, a third electric circuit connectedbetween'isaid grid and said cathode and including .meansin said firstcircuitresponsive to current flow'between said anode andlsaid cathodefor supplying a potential hetweensaid grid. andlsaidlcathode which is180 out ofiphase withlthe potential appearing. between fsaid anode l andsaid 1 cathode, electrical conductor means having a first .end portioncone nected to saidlanode, said conductor means having an electricallength such that its otherend portion is electrically spaced from saidoneend portion an electrical distancenot less than onequarterof thelength. of theoutput wave of said valve whereby said conductor means isprovided with a node point in which the voltage thereof with respect tosaid cathode is zero, a variable impedance having a pair of terminals,means connecting one of said terminals to said conductor, meansconnecting the other of said pair of terminals to said cathode, andmeans connected between said conductor and said cathode to measure thevoltage between said cathode and the point of connection of saidlast-named means to said conductor.

8. In an electrical measuring system for determining the magnitude of acharacteristic of a workpiece, means for generating an oscillatoryelectric wave, means providing a circuit having the characteristics ofan electrical conductor of a length not less than one-quarter of thelength of said generated wave whereby a standing wave will be producedin said second named means, means operable in accordance with themagnitude of the workpiece characteristic for varying a characteristicof said generated wave, and means responsive to the changedcharacteristic of said wave for determining the magnitude of theworkpiece characteristic.

9. In an electrical measuring system for determining the magnitude of acharacteristic of a workpiece, means for generating an oscillatoryelectric wave, means providing a circuit having the characteristics ofan electrical conductor of a length not less than one-quarter of thelength of said generated wave whereby a standing wave will be producedin said second named means, means operable in accordance with themagnitude of the workpiece characteristic for varying the wave length ofsaid generated wave, and means connected to said network at a fixedphysical location and operable to measure the potential at said fixedlocation.

10. In an electrical measuring system for determining the magnitude of acharacteristic of a workpiece, means for generating an oscillatoryelectric wave, a network connected to said means for receiving said waveand having substantially the electrical characteristics of a conductorof a length not less than one-quarter of the length of said wave, saidgenerating means being sensitive to the impedance of said conductor, apair of plates forming a condenser, means for moving one of said plateswith respect to the other or said 22 plates in accordance with changesin magnitude of said characteristic, one of the plates of said condenserbeing connected to said conductor and the other of said plates beingconnected to said first named means, said condenser being of suchcapacity as to bring the frequency of said wave to the maximum desiredfrequency when said plates are spaced apart, said condenser acting tolower the frequency of said wave as said platesare moved by said movingmeans into a closer relative position, and means responsive to thechange in amplitude of said wave at a fixed point in said conductor fordetermining the magnitude of said characteristic.

11. The combination of claim 10 in which the employed portion of thecharacteristic curve of said condenser and the employed portion of theresonant voltage curve are substantially complemental to one anotherwhereby a substantially linear change in amplitude results from linearchange in spacing of said plates.

12. The combination of claim 11 in which means is provided to adjust themagnitude of the energy transmitted by the generating means in saidfirst named network and for adjusting the Q of the generating means andof said first named network whereby said supplied energy and said Q maybe controlled to further render said amplitude change linear withrespect to relative movement of said plates.

MAX M. ARLIN.

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